Lever operated electric switches



Jan. 10, 1961 E. GREAVES LEVER OPERATED ELECTRIC SWITCHES Filed June 1,1959 2 Sheets-Sheet 1 /N VEN To@ fa//V//V 655/: 1/55 A 7' 70E/VE Y Jan.10, 1961 E. GREAVES 2,967,919

LEVER OPERATED ELECTRIC SWITCHES Filed June 1, 1959 2 Sheets-Sheet 2United States LEVER OPERATED ELECTRIC SWITCHES Edwin Greaves,Longlevens, Gloucester, England, as-

slgnor to Dowty Nucleonics Limited, Andoversford, England, a Britishcompany This invention relates to lever-operated electrical switches foruse where it is desirable, firstly that under some conditions of use theswitch should be locked against operation and under other conditions ofuse should be easily operable, and secondly that when in the lockedposition some method of emergency operation is possible. An example ofsuch a switch is that used to control lowering or raising of an aircraftundercarriage, it being normally desirable to lock the switch when theaircraft is on the ground to prevent raising of the undercarriage. If,during taxiing or take-off, it be comes necessary to stop the aircraftvery quickly, for example to avoid a collision, it is necessary to raisethe undercarriage to drop the aircraft on to the ground to effectstopping in the shortest possible distance. Such raising of theundercarriage would then need to be effected by moving the switchagainst the lock.

The main object of the present invention is to provide a lever switch inwhich the movement to overcome locking of the lever under emergencyconditions is by twisting the lever about its longitudinal axis. Afurther object of the invention is to provide a simple construction oflever switch in which the lever twisting action for emergency operationis accomplished by a small angle of twisting, for example about 50,which is easily rattainable by an operator at one turn of the hand.

A still further object is to provide, a lever-operated electric switchcapable of being locked against normal operation by a movable pawlengageable with the lever within the switch, the lever being providedwith a projection adjacent to the pawl which, on twisting of the lever,engages the pawl to move it out of locking engagement with the lever.Preferably, the twisting action is resisted by spring loading carriedwithin the lever and reacting against the normal pivotal fulcrum of thelever. The pawl preferably comprises an armature of an electromagnetwhich moves into the locking position when no current is passing throughthe electromagnet.

One example of the invention will now be described with reference to theaccompanying drawings, in which:

Figures 1 and 2 are cross-sections through the switch at right-angles toone another;

Figure 3 is a cross-section showing the structural framework of theswitch; and

Figure 4 is a detailed view on the line lV-lV of Figure 1.

The switch casing comprises a gate member 1 and an insulating basemember 2 which are located at opposite ends of a metallic shell 3.Within the casing a framework is located between the gate and the basemembers 1 and 2 comprising four metal bars 4 extending between the gatemember 1 and base member 2, a pair of upper cross members 5 securedbetween the bars 4 and a pair of intermediate cross members 6 alsosecured between the bars 4. The switch operating lever is thecombination of a metallic bush 7 and a rod 8 extending through ice i tothe upper cross members 5 by means of pivots 11, these pivots engagingthe wall only of the bush and not projecting into the bore 9. The gatemember 1 comprises a lower member 12 directly secured to the bars 4 andan upper member 13 secured to the lower member 12. The lower member 12includes a slot 14 within which the upper end of the bush 7 moves duringpivotal movement about pivots 11. Centrally disposed within the slot 14a pair of spring-loaded balls 15 are located within co-axial bores 16extending parallel to the pivot axis of pivots 11. The balls 15 engagethe upper end of the bush 7 and serve to urge the bush in its pivotalmovement either to one end or the other of slot 14. The rod 8 extendsupwardly from the bush 7 and at its outer end a circular operatingbutton 17 is secured, the longitudinal axis of rod 8 extending along adiameter of the button 17. The purpose of the button is to enable therod 8 to be twisted about its longitudinal axis. On the rod 8 betweenthe upper end of bush 7 and the button 17 a cup 18 is mounted by meansof a hollow cylindrical portion 19 which is a sliding iit on the rod 8.A compression spring 21 acting between the button 17 and the cylindricalportion 19 urges the cup towards the upper end of the bush 7. The lowerend of the cylindrical extension 19 iits within a slot 22 formed in theupper member 13. This slot is narrow at 4its central position 23 and ateither end includes a circular enlargement 24 to receive the end of thecylindrical portion 19. Thus, the cylindrical portion 19 can engageeither of the circular enlargements 24 and forms an auxiliary lock onthe lever in either extreme position, it being necessary to lift the cupbefore the lever can be moved from either extreme position.

The rod 8 at the upper end of bush 7 is formed with an enlargement 25which engages a shoulder 26 within bore 9 whilst at its lower end itincludes a transversely extending pin 27. The lower end of the bushincludes a pair of diametrically opposed projections 28 which cooperatewith the pin 27 to form stops on the twisting movement of the rod 8within bush 7 to allow a total angular movement of about 50 of rod 8about its longitudinal axis. Within the walls of the bush 7 at its lowerend a pair of spring-loaded balls 29 are provided mounted in bores 31within'the bush and extending parallel to the longitudinal axis of therod 8. The balls 29 co-operate with the pin 27 vto urge it to either oneor other extreme of angular twisting movement of the pin between thestops 28.

A platform 32 is supported interiorly of the switch from two bars 4 bymeans of supports 33, this platform carrying a yoke 34, anYelectromagnet windingor solenoid 35 and an electromagnet core 36. Withinan opening 37 in the platform an electromagnet armature 38 is pivotallymounted, an extension 39 of this armature carries a counterbalanceweight 41 and is acted upon by a compression spring 42 which serves tourge armature 38 away from the core 36. The free end 43 of the armature,when urged away from the core 36 by spring 42, engages with a groove 44around the lower end of rod 8 when the lever is in the position shown inFigure l `to lock the lever against movement about its pivots 11.

In the position of the rod in Figure l the plane of the button 17 liesin the plane of pivotal movement of the lever and the pin 27 occupies aninclined position against stops 28. If the button 17 is twisted the pin27 will move with the rod 8 about the rods longitudinal axis so that thepin moves to its opposite position against stops 28 where thelongitudinal axis of the pin lies in the plane of pivotal movement ofthe lever about pivot 11. In this movement one end of the pin 27 willengage against the upper surface of the armature 38 to depress out ofengagement with the groove 44 thus removing the lock on movement of thelever so that it may be moved to its opposite position.

The base 2 is provided with four sets of identical contacts which`co-operate with four identical sliding contacts. For convenience, onlyone set of these contacts and one sliding contact will be described.Each set of contacts comprises a pair of fixed end contacts 45 and 46and a central contact 47 located within a channel 48 formed within thebase 2. The sliding contact comprises a strip of metal 49 whose lengthis suicient to bridge from the centre contact 47 to one or the other ofthe outer contacts, this strip 49 being carried by a carrier 51 of aninsulating material. The carrier 51 is channel-shaped, the strip 49being carried by the base thereof and located by tangs 52 at the end ofthe strip which engage in small recesses in the carrier 51. The carrier51 is located in position by sliding engagement within the channel 43and is spring-urged on to the fixed contacts by means of fa springformed of steel wire 53 which engages a small projection 54 locatedcentrally of the upper side of the carrier 51. `Steel wire 53 beforeinsertion in the switch is straight, but during insertion it is clampedin position by means of insulating plates 55 and 56 engaging the ends ofthe steel wire 53 and locating them in recesses '7 and 5S in the base 2.In the clamping of the wire it is elastically bent .by its engagementwith the projection 54 whereby the wire 53 will exert a resilient forceon the carrier 51 through the projection 54 thus causing the movingcontact strip 49 to be held resiliently in contact with the fixedcontacts in the base 2. Each contact carrier has two side members 59extending upwardly and in each a vertically directed slot 61 is formed.A contact moving pin 62 extends transversely in the slots 61 of allcontact carriers, moving them simultaneously. Movement is applied to thepin 62 by means of a pair of auxiliary levers 63 located one on eachside of the switch and pivoted in the members 6 of the framework bypivot pins 64. The auxiliary levers 63 include slots 65 at their upperends for engagement with pins 66 extending one from either side of thelower end of bush 7. In this way it will be seen that angular movementof the operating lever will cause opposite angular movement of theauxiliary lever 63 to impart linear sliding movement to the contactcarriers 51 within their grooves 48. It is arranged that at one Vextremeposition of the operating lever within slot 14 the moving contact strips49 bridge the fixed contacts 45 and 47 whilst in the other extremeposition of the operating lever the moving contact strip 49 bridges thefixed contacts 46 and 47.

Within the underside of the base 2 a plurality of screw connectors 67are located by which electric cables may he connected to the fixedcontacts. A rubber cover 68 encloses the base 2 tocover vthe connectionsbetween electric cables to the screw connectors 67.

For normal operation in controlling the undercarriage of an aircraft,the switch inthe position `as shown in Figure l corresponds to theundercarriage in its lowered position and an electric circuit throughthe electromagnet lwinding 3S is arranged to `be opened when aircraftweight is on the aircraft landing wheels compressing the undercarriageto some extent. Breaking-of this electric circuit allows the armature 38to lift'into the position shown to act as a pawl and engage the groove44 on rod 8 thus preventing operation of the lever to raise theundercarriage. When the aircraft has taken offand weight is then removedfrom the landing wheels-` an electric circuit is established through thewinding 3S to attract armature 38 to core 36 and thus to remove the lockon the lever to allow it to be moved to a position to cause theundercarriage to be raised. When the aircraft is on the ground and, forexample is taxiing, yand emergency conditions arise rendering itnecessary to raise the undercarriage, for example in order to avoid acollision, the pilot of the aircraft twists the button 17 to twist therod 8 causing one end of the transverse pin 27 to engage armature 38 andmove it out of locking engagement with the groove 44. The switch maythen be moved in the normal way to raise the undercarriage allowing thei'rcraftto fall o'n the ground and to stop as q`uickly as possible. Theone end of the transverse pin forms a projection to engage the armatureto move it from the locked position.

It is desirable, after the button 17 has been twisted for emergencylifting of the undercarriage, that it should not be possible to twistthe button back to its normal position whereby it is possible toestablish at a later date that the reason for raising the undercarriagewas due to a definite emergency action on the part of the pilot. Forthis purpose, an addition may be made to the switch as shown in thecross-section at Figure 4. In this crosssection the enlargement 25 ofthe rod located in the upper end of the bush 7 is provided with atransversely extending recess 69 within which a spring-loaded plunger 71is located having an outer end 72 of reduced diameter. A slot 73 is cutacross the end of bush 7 such that in the normal position of button 17the reduced end 72 of plunger 71 is out of register with slot 73, but sothat when button 17 is twisted for emergency operation the end 72 ofplunger 71 will engage in slot 73 to prevent thefrod being twisted backto its normal position.

For adjustment of the effective position of armature 38 to engage groove44 the platform 32 carrying the e1ectromagnet assembly is arranged forlimited vertical adjustment on supports 33 by virtue of elongated holesin the platform through which fixing screws to the supports 33 extend.

In order to prevent entry of dust and the like into the switch a rubbercover 74 may be provided internally of the switch clamped under themember 12 and engaged around a recess 75 inthe bush 7.

I claim as my invention:

l. A lever-operated electric switch comprising a switch casing, a levermounted in the casing for pivotal switch operating movement about anaxis transverse to its longitudinal axis and for twisting movement aboutits longitudinal axis, a pawl movably mounted in the casing and capableof locking the lever when in one switch operating position to preventpivotal movement to another switch operating position and a projectioncarried bythe lever within the casing and movable on twisting movementof the lever to engage the pawl to unlock the lever to permit pivotalmovement thereof to another switch operating position.

2. A lever-operated electric switchcomprising a switch casing; a levermounted in the casing for pivotal switch operating movement about anaxis transverse to its longitudinal axis and for twisting movement aboutits longitudinal axis; said lever comprising a bush pivotally mounted inthe casing about an axis transverse to the axis of the Ybore within thebush, a rod carried in the bore of the bush so as to be capable oftwisting movement and a handle at the outer end of the rod wherebytwisting movement may be applied to the' rod; a` pawl movably mounted inthe casing to engage the lever when in one switch operating position toprevent pivotal movement to another switch operating position; and aprojection carried by the lever within the casing and movable ontwisting movement of the lever to engage the pawl to move it out oflocking engagement with `the lever.

3. A lever-operated electric switch as claimed in claim 2, including aspring-loaded plunger located within the bush for co-operation withinthe projection to ensure that a predetermined twisting torque must beapplied to the rod in order to bring the projection into switchunlocking engagement with the pawl.

4. A lever-operated electric switch as claimed in claim 3, wherein therod is located against endwise movement within the bush by engagement ofthe projection with one end of the bush and by engagementof a ange onthe bush with a shoulder in the bore of the bush.

5. A lever-operated electric switch as claimed in claim 4, wherein therod within the bush includes a transversely disposed spring-loadedplunger arranged to engage a recess in the hush when the rod is twistedto unlock the switch thereby preventing the rod being twisted back tothe switch locked position.

6. A lever-operated electric switch comprising a switch casing, a levermounted in the casing for pivotal switch operating movement about anaxis transverse to its longitudinal axis and for twisting movement aboutits longitudinal axis, a pawl movably mounted in the casing to engagethe lever when in one switch operating position to prevent pivotalmovement to another switch operating position, a projection carried bythe lever within the casing and movable on twisting movement of thelever to engage the pawl to move it out of locking engagement with thelever, an electromagnet, and a pivoted armature for the electromagnet,this armature forming the pawl engageable with the lever whereby lockingof the switch depends on energization of the electromagnet.

7. A lever-operated electric switch comprising a switch 20 casing, alever mounted in the casing for pivotal switch operating movement aboutan axis transverse to its longitudinal axis and for -twisting movementabout its longitudinal axis, a pawl movably mounted in the casing toengage the lever when in one switch operating position to preventpivotal movement to another switch operating position, a projectioncarried by the lever within the casing and movable on twisting movementof the lever to engage the pawl to move it out of locking engagementwith the lever, xed contacts, an insulating support carrying the fixedcontacts, a sliding Contact co-operating with the xed contacts, springloading urging the sliding contact against the xed contacts and anoperative connection between the lever and the sliding contact.

8. A lever-operated switch as claimed in claim 7, wherein the springloading comprises a strip o-f spring material extending substantiallyparallel to the path of movement of the sliding contact and elasticallybent t0 engage the sliding contact with resilient force over the path ofmovement.

9. A lever-operated switch as claimed in claim 8, wherein the strip ofspring material in its normal unstressed state is straight and thesupport in which the lixed contacts are mounted includes a pair ofclamps to grip the two ends of the strip with its intermediate portionin touching the moving contact so that the strip is elastically bent andexerts resilient force on the sliding contact.

10. A lever-operated switch -as claimed in claim 9, wherein theoperative connection between the sliding contact and the lever comprisesa pair of spaced auxiliary levers between which the pawl is mounted toco-operate with the switch operating lever.

1l. A lever-operated switch as claimed in claim l0, including anelectromagnet and a pivoted armature for the electromagnet which formsthe pawl, both the electro- References Cited in the tile of this patentUNITED STATES PATENTS Koch Sept. 30, 1952 Arda Feb. 14, 1956

